JP7339543B2 - plastic container - Google Patents

Description

The present invention relates to plastic containers.

Patent Literature 1 discloses a plastic container for oily contents that has good slipping properties when storing oily substances such as calorie-free mayonnaise containing a thickener.

JP 2016-190654 A

In Patent Literature 1, a resin composition in which silicone is added to polyolefin is used to form the innermost layer of a container, thereby improving the slipping property of the oily substance.

However, when the plastic container of Example 1 of Patent Document 1 was stored at room temperature for a long period of time, it was found that a phenomenon occurred in which the sliding-down property of the contents was remarkably reduced.

SUMMARY OF THE INVENTION The present invention has been made in view of such circumstances, and provides a plastic container in which contents can be easily slipped off even after long-term storage.

According to the present invention, there is provided a plastic container for containing contents, comprising an innermost layer, an intermediate layer, and an outermost layer in order from the inner surface of the container, wherein the innermost layer and the outermost layer are made of a thermoplastic resin. The intermediate layer is composed of a resin composition containing a thermoplastic resin, a fatty acid amide, and a migration inhibitor, and the migration inhibitor prevents the fatty acid amide from migrating to the innermost layer A plastic container is provided that inhibits

When the reason why the plastic container of Example 1 of Patent Document 1 deteriorates in sliding property after long-term storage was investigated, the repro layer arranged adjacent to the innermost layer contained the fatty acid amide-based fatty acid contained in the outermost layer. It was found that the fatty acid amide contained in the repro layer bleeds out to the surface of the innermost layer during long-term storage, and the fatty acid amide prevents the oily substance from sliding down.

Based on this finding, when fatty acid amide is contained in a layer located between the innermost layer and the outermost layer, the layer contains a transfer inhibitor that suppresses the transfer of fatty acid amide to the innermost layer. found that the migration of the fatty acid amide to the innermost layer is suppressed, and as a result, the inhibition of the fatty acid amide from sliding down of the contents is suppressed, leading to the completion of the present invention.

Various embodiments of the present invention are illustrated below. The embodiments shown below can be combined with each other.
Preferably, in the plastic container described above, the migration inhibitor is composed of a substance incompatible with the thermoplastic resin of the intermediate layer.
Preferably, the plastic container described above, wherein the migration inhibitor comprises silicone.
Preferably, the plastic container as described above, wherein the intermediate layer is positioned adjacent to the innermost layer.
Preferably, in the plastic container described above, the resin composition forming the innermost layer contains an additive other than the fatty acid amide.
Preferably, the plastic container described above, wherein the additive is a polyhydric alcohol fatty acid ester.
Preferably, in the plastic container described above, the resin composition constituting the outermost layer contains a fatty acid amide, and the intermediate layer is a repro layer composed of a resin composition containing a repro material. is a container.

1 is a front view showing a plastic container 1 and a cap 13; FIG. 1 is a layer configuration diagram of a plastic container 1. FIG.

Embodiments of the present invention will be described below. Various features shown in the embodiments shown below can be combined with each other. In addition, the invention is established independently for each characteristic item.

1. Composition of plastic containers

FIG. 1 shows a schematic diagram of a plastic container 1 of one embodiment of the present invention. As shown in FIG. 1, a container 1 is a container for containing contents. The content is not particularly limited, but if it is a substance (preferably an oily substance) containing a thickening agent such as calorie-free mayonnaise, the slipping property tends to decrease after long-term storage, so such a substance should be used as the content. The technical significance of applying the present invention is particularly great in the case of objects.

The container 1 has a spout 12 formed with a screw thread 11, and the contents are squeezed out by squeezing the barrel 14 and the like. Normally, the spout 12 is sealed with a cap 13 attached. . The container 1 is a blow molded body formed by blow molding. The details of blow molding will be described later.

The container 1 has a multilayer construction. FIG. 2 shows an example of the layer structure of the container 1. From the inner surface side of the container 1, the innermost layer 2, the intermediate layer 3, the adhesive resin layer 4, the barrier layer 5, the adhesive resin layer 6, and the outermost An outer layer 7 is provided. The layer construction of the container 1 may omit at least one of these layers, or may comprise additional layers.

For example, the thickness ratio of each layer is as follows.
Innermost layer 2: 10-30%
Intermediate layer 3: 30-60%
Adhesive resin layer 4: 0.3 to 5%
Barrier layer 5: 3-8%
Adhesive resin layer 6: 0.3 to 5%
Outermost layer 7: 20-40%

Each layer will be described below.

(Innermost layer 2)
The innermost layer 2 is a layer in contact with the contents, and is composed of a resin composition containing a thermoplastic resin. The thermoplastic resin is preferably polyolefin. As the polyolefin, it is preferable to use polyethylene or polypropylene, and it is particularly preferable to use polyethylene. It is preferable to use polyethylene or polypropylene as the main component in the resin component, and it is particularly preferable to use polyethylene as the main component in the resin component. As polyethylene, it is preferable to use low-density polyethylene (LDPE) or linear low-density polyethylene (LLDPE) in consideration of transparency, squeezability (squeezability), and the like.

Preferably, the resin composition forming the innermost layer 2 does not substantially contain fatty acid amide. Since the fatty acid amide is a compound having a lipophilic group and has a high affinity for oily contents such as mayonnaise, there are cases where the fatty acid amide rather reduces the sliding property for oily contents. I don't like it because In addition, "substantially free" means that these are not intentionally added, and does not necessarily mean that they are not included at all. It is allowed to contain trace amounts. The specific content is preferably less than 0.1% by mass, more preferably less than 0.01% by mass, and particularly preferably not contained at all with respect to the entire innermost layer 2 .

The resin composition forming the innermost layer 2 may contain additives other than the fatty acid amide. Addition of additives can be expected to improve the slideability of contents.

Polyhydric alcohol fatty acid esters are preferred as additives. It preferably contains a polyhydric alcohol fatty acid ester. The polyhydric alcohol fatty acid ester preferably has at least three hydroxyl groups and is not fully esterified. Moreover, from the viewpoint of bleeding out from the container, it is preferably a polyhydric alcohol fatty acid ester having a valence of less than 10. The polyhydric alcohol fatty acid ester that satisfies the above conditions has good bleed-out properties, and also has good slipping properties against contents, especially contents made viscous by adding a thickening agent such as thickening polysaccharide. , and the content discharge performance can be maintained satisfactorily. This is because the presence of both an ester group and a hydroxyl group can provide good lubricity to a content to which a thickener has been added. As such a polyhydric alcohol fatty acid ester, a diglycerol fatty acid ester having an esterification rate of 10 to 40% is particularly preferable from the viewpoint of bleeding out property and lubricity for a content containing a thickener.

Saturated fatty acids include stearic acid and lauric acid. Moreover, oleic acid etc. are mentioned as an unsaturated fatty acid.

The content of polyhydric alcohol fatty acid ester is preferably in the range of 0.05 to 5% by weight, particularly 0.1 to 1% by weight. That is, if the amount is less than this range, the amount that bleeds out to the surface of the innermost layer 2 is small, so good slipperiness is not imparted, and therefore the transportability of the container is also lowered. On the other hand, if the amount is more than the above range, the amount of bleed-out is too large, which may stain the line during container molding or affect the taste of the contents.

(Outermost layer 7)
The outermost layer 7 is a layer arranged on the outermost side of the container, and is composed of a resin composition containing a thermoplastic resin. A preferable thermoplastic resin is the same as that of the innermost layer 2, and it is preferable that the thermoplastic resins constituting the innermost layer 2 and the outermost layer 7 are the same.

The resin composition forming the outermost layer 7 preferably contains a fatty acid amide. Addition of fatty acid amide makes it possible to exhibit slipperiness according to various environmental temperatures in each process from molding of the container 1 to filling of contents, transfer, and packaging, and the surface of the container 1 does not slip easily in each process. etc. can be eliminated. For the outermost layer 7, for example, a resin obtained by adding, mixing and kneading a fatty acid amide into a thermoplastic resin in order to impart lubricity to a food filling line or the like which is mainly composed of a metal material such as stainless steel. Preference is given to using compositions.

A saturated fatty acid amide or an unsaturated fatty acid amide can be used as the fatty acid amide. Saturated fatty acid amides include butyramide, hexylamide, decylamide, lauric acid amide, myristic acid amide, palmitic acid amide, and stearic acid amide. Among these saturated fatty acid amides, it is preferable to use stearic acid amide. These saturated fatty acid amides may be used singly or in combination of two or more.

Examples of unsaturated fatty acid amides include acrylamide, methacrylamide, crotonamide, isocrotonamide, undecylenic acid amide, cetoleic acid amide, oleic acid amide, erucic acid amide, ethylenebisoleic acid amide, oleyl palmitamide, stearyl erucamide, linoleic acid amide, linolenic acid amide, arachidonic acid amide, and the like. Among these, those having 14 to 24 carbon atoms, such as cetylamide, oleic acid amide, erucic acid amide, linoleic acid amide, linolenic acid amide, arachidonic acid amide, etc., are preferably used. Particular preference is given to using acid amides. These unsaturated fatty acid amides may be used alone or in combination of two or more.

The content of the fatty acid amide in the outermost layer 7 is preferably 0.01 to 10 mass % with respect to the entire resin composition forming the outermost layer 7 . By setting the amount of the fatty acid amide to be added within such a range, it is possible to exhibit good lubricity. Fatty acid amide is particularly preferably 0.1 to 5 mass % with respect to the entire resin composition constituting the outermost layer 7 .

(Intermediate layer 3)
The intermediate layer 3 is arranged between the innermost layer 2 and the outermost layer 7 . The intermediate layer 3 is composed of a resin composition containing a thermoplastic resin, a fatty acid amide, and a migration inhibitor.

The intermediate layer 3 is preferably made of a resin composition containing a repro material obtained by recycling scrap generated when the container 1 is molded. Since all the layers of the container 1 are included in the scrap, the repro material is a mixture of the resin compositions forming each of the layers of the container 1 . When the outermost layer 7 contains fatty acid amide, the repro material inevitably contains fatty acid amide, and the intermediate layer 3 made of the resin composition containing this material also inevitably contains fatty acid amide.

The resin composition forming the intermediate layer 3 is preferably a mixture of a repro material and a virgin thermoplastic resin. In this case, from the viewpoint of recycling resources while maintaining moldability, the amount of repro is 10 to 60 parts by weight per 100 parts by weight of the virgin thermoplastic resin (for example, the thermoplastic resin of the innermost layer 2). It is preferable to make it about a part. The resin composition forming the intermediate layer 3 may not contain the repro material. In this case, the thermoplastic resin, the fatty acid amide, and the migration inhibitor are mixed to form the resin composition.

Virgin thermoplastics include bio-polyethylene. The density of the bio-polyethylene is preferably higher than that of the polyethylene of the outermost layer 7 , and more preferably higher than that of the polyethylene of the innermost layer 2 . The higher the density, the more the bleed-out is suppressed, so migration of the fatty acid amide to the innermost layer 2 can be delayed.

If the intermediate layer 3 contains fatty acid amide, the fatty acid amide may migrate to the innermost layer 2 during long-term storage and bleed out from the surface, thereby reducing the slipping property of the contents. Therefore, in the present embodiment, the migration inhibitor is contained in the intermediate layer 3 to suppress the migration of the fatty acid amide to the innermost layer 2, thereby suppressing the drop property.

The migration inhibitor is a substance that has a function of suppressing the migration of fatty acid amide to the innermost layer 2 . The migration inhibitor preferably suppresses the migration by a labyrinth effect. The labyrinth effect means an effect that the transfer inhibitor forms a labyrinth-like structure in the intermediate layer 3 and the fatty acid amide enters into this structure, thereby suppressing the transfer of the fatty acid amide.

The migration inhibitor is preferably composed of a substance incompatible with the thermoplastic resin of the intermediate layer 3 . This is because in this case, the labyrinth effect is likely to be exhibited.

Polymers such as silicone and fibrous or particulate fillers are preferable as migration inhibitors. This is because in either case, the effect of suppressing movement due to the maze effect can be exhibited.

Examples of fillers include inorganic particles and inorganic fibers. Inorganic particles include silica, alumina, titanium oxide, zinc oxide and the like. Examples of inorganic fibers include carbon fibers and glass fibers.

Examples of silicones include organopolysiloxanes, which may have a linear (linear) or partially branched molecular structure. Among organopolysiloxanes, diorganopolysiloxanes may be used. is preferred.

The weight average molecular weight (M _w ) of the silicone is preferably one million (1,000,000) or more. This is because when the weight average molecular weight of the silicone is 1,000,000 or more, the labyrinth effect is likely to be exhibited remarkably. It is particularly preferable that the weight average molecular weight of the silicone is one million (1,000,000) to ten million (1,0000,000). In addition, the weight average molecular weight can be measured by a conventionally known method such as gel filtration chromatography.

The viscosity of the silicone is preferably 6 million (6,000,000) cS or more, particularly preferably 6,000,000 to 10,000,000 (1,0000,000) cS.

The content of silicone is preferably 0.001 to 15.0% by mass with respect to the entire resin composition forming the intermediate layer 3 . By setting the amount of the lubricant to be added in such a range, good sliding performance can be exhibited. The lubricant is more preferably 0.05 to 6.0% by mass, more preferably 0.1 to 6.0% by mass, more preferably 0.2 to 5.0% by mass with respect to the entire layer 2 is particularly preferred. In addition, silicone may be used as a masterbatch (MB) mixed with a base resin made of polyolefin such as polyethylene or polypropylene resin or other resin. The silicone content is 10 to 70% by mass with respect to the entire masterbatch). It is preferable to add 0.01 to 20% by mass, particularly preferably 0.5 to 8.0% by mass, but the range is not particularly limited.).

The migration inhibitor contained in the intermediate layer 3 may be derived from the repro material, or may be added separately.

The content of the fatty acid amide in the intermediate layer 3 is preferably 0.001 to 10 mass % with respect to the entire resin composition forming the intermediate layer 3 . Specifically, this content is, for example, 0.001, 0.01, 0.02, 0.05, 0.1, 0.2, 0.5, 1, 2, 5, 10% by mass. , within a range between any two of the numerical values exemplified herein. In this case, the technical significance of suppressing migration by adding a migration inhibitor is significant.

The intermediate layer 3 is preferably arranged adjacent to the innermost layer 2 . In such an arrangement, the fatty acid amide in the intermediate layer 3 is likely to migrate to the innermost layer 2, so the addition of a migration inhibitor to suppress migration is of considerable technical significance.

(Barrier layer 5)
The barrier layer 5 is made of a resin having a high gas barrier property. Examples of such resin include ethylene vinyl alcohol copolymer (EVOH: saponified ethylene vinyl acetate copolymer, etc.) and aromatic polyamide. By providing the barrier layer 5, it is possible to effectively suppress oxidative deterioration of the contents due to permeation of oxygen.

The barrier layer 5 is preferably arranged between the intermediate layer 3 and the outermost layer 7 . In this case, migration of fatty acid amide from the outermost layer 7 to the intermediate layer 3 can be suppressed. In addition, by arranging the barrier layer 5 closer to the outermost layer 7 than the intermediate layer 3, it is possible to prevent the relative humidity of the barrier layer 5 from increasing due to the moisture content. Since EVOH has a higher oxygen permeation rate as the relative humidity increases, placing the barrier layer 5 closer to the outermost layer 7 than the intermediate layer 3 can suppress an increase in the oxygen permeation rate.

(Adhesive resin layers 4 and 6)
The adhesive resin layers 4 and 6 are made of an adhesive resin. Examples of adhesive resins include acid-modified polyolefin resins (eg, maleic anhydride-modified polyethylene, maleic anhydride-modified polypropylene) and the like. By providing the adhesive resin layers 4 and 6, the adhesion between the barrier layer 5 and the outermost layer 7 or the intermediate layer 3 is improved. Instead of providing the adhesive resin layers 4 and 6, the barrier layer 5 may contain an adhesive resin.

2. Method of manufacturing a plastic container The container 1 can be formed by blow molding a parison. The blow molding may be direct blow molding or injection blow molding. In direct blow molding, the container 1 is manufactured by sandwiching a molten cylindrical parison extruded from an extruder between a pair of split molds and blowing air into the parison. In injection blow molding, a test tube-shaped bottomed parison called a preform is formed by injection molding, and blow molding is performed using this parison.

The layer structure of the parison is the same as the layer structure of the container 1 in any blow molding. A multilayer parison can be formed by coextrusion molding, multilayer injection molding, or the like.

When the container 1 is formed by direct blow molding, the portion of the cylindrical parison within the cavity formed by the pair of split molds becomes the container 1, and the portion other than the container 1 becomes scrap. This scrap contains the constituent materials of all the layers that make up the container 1 . A repro material is obtained by subjecting this scrap to recycling treatment such as pulverization.

1. Production of Container 1 A container 1 having the shape shown in FIG. 1 and the layer structure shown in FIG. 2 and Table 1 was produced. The container 1 was manufactured by extruding a cylindrical parison from a multi-layer die head by co-extrusion molding of the constituent resins or resin compositions, followed by known direct blow molding. The numerical values of the silicone MB and the additive MB in Table 1 mean mass % of the total resin composition constituting each layer. The thickness of the container 1 (thickness of the body) is 200 μm as a whole, and the thickness ratio of outermost layer 7/adhesive resin layer 6/barrier layer 5/adhesive resin layer 4/intermediate layer 3/innermost layer 2 is 200 μm. were, in order, 30/1.5/3.0/1.5/54/10.

Details of the compositions in Table 1 are as follows.
LDPE containing oleic acid amide: 0.1% by mass of oleic acid amide in the LDPE base material.
Silicone MB: Silicone masterbatch, containing 50% by weight of silicone in an LDPE base. The silicone has a weight average molecular weight of one million (1,000,000) or more and a viscosity of six million (6,000,000) cS or more.
Additive MB: A masterbatch obtained by mixing LDPE and diglycerin laurate at a mass ratio of 90:10.

2. Evaluation of Sliding Property The obtained container was allowed to stand in a constant temperature bath at 50° C. for 3 weeks, and then the sliding property was evaluated according to the following criteria. The results are shown in Table 1 together with the layer structure of the container.

100 g of calorie-free mayonnaise was placed in a container (capacity: 500 g) as an oily content, and the container was turned upside down once to move most of the content (mayonnaise) to the top side (the side with the cap). After being moved, it was returned from the upside down position to the upright position, placed in a refrigerator, and stored for 12 hours. After 12 hours, 90% or more (90 g or more) as a mass ratio is present from the bottom of the container to the position of 1/5, "○", 70% or more and less than 90% (70 g or more and less than 90 g) is present The case was evaluated as “Δ”, and less than 70% (less than 70 g) as “×”.

As shown in Table 1, in Reference Example 1, in which the intermediate layer 3 did not contain a fatty acid amide, the sliding property was excellent. On the other hand, in Comparative Examples 1 to 3 in which the intermediate layer 3 contained a fatty acid amide and did not contain a migration inhibitor, the slide down property was not good. On the other hand, in Example 1, in which the intermediate layer 3 contained silicone as a migration inhibitor, the sliding property was good in spite of the fact that the intermediate layer 3 contained fatty acid amide.

Reference Signs List 1: Plastic container 2: Innermost layer 3: Intermediate layer 4: Adhesive resin layer 5: Barrier layer 6: Adhesive resin layer 7: Outermost layer 11: Thread 12: Spout 13: Cap 14: Body

Claims (7)

A plastic container containing contents,
An innermost layer, an intermediate layer, and an outermost layer are provided in order from the inner surface of the container,
The innermost layer and the outermost layer are composed of a resin composition containing a thermoplastic resin,
The intermediate layer is composed of a resin composition containing a thermoplastic resin, a fatty acid amide, and a migration inhibitor,
The plastic container, wherein the migration inhibitor suppresses migration of the fatty acid amide to the innermost layer. A plastic container according to claim 1,
The plastic container, wherein the migration inhibitor is composed of a substance incompatible with the thermoplastic resin of the intermediate layer. The plastic container according to claim 1 or claim 2,
The plastic container, wherein the migration inhibitor contains silicone. The plastic container according to any one of claims 1 to 3,
The plastic container, wherein the intermediate layer is positioned adjacent to the innermost layer. The plastic container according to any one of claims 1 to 4,
A plastic container, wherein the resin composition constituting the innermost layer contains an additive other than the fatty acid amide. A plastic container according to claim 5,
The plastic container, wherein the additive is a polyhydric alcohol fatty acid ester. The plastic container according to any one of claims 1 to 6,
The resin composition constituting the outermost layer contains a fatty acid amide,
The plastic container, wherein the intermediate layer is a repro layer made of a resin composition containing a repro material.